3.log(3X-5)=0

3x-5=0

3x-5=1    x=2

6.log(x2次+1)2次=2

    2logx2次=2

     logx2次+1=4

     x2次=4-1

      開方x2次=3

        x=+-3

7.logx+log4=log48

log(4.x)=log48

log4x=log48

xlog4/log4=log48/log4

x=12

14.5X=20

log5x=log20

xlog5=log20

xlog5/log5=log20/log5

x=1.86